Handheld sensing apparatus

ABSTRACT

A vapor sensing device that is sufficiently small and lightweight to be handheld, and also modular so as to allow the device to be conveniently adapted for use in sensing the presence and concentration of a wide variety of specified vapors. The device provides these benefits using a sensor module that incorporates a sample chamber and a plurality of sensors located on a chip releasably carried within or adjacent to the sample chamber. Optionally, the sensor module can be configured to be releasably plugged into a receptacle formed in the device. Vapors are directed to pass through the sample chamber, whereupon the sensors provide a distinct combination of electrical signals in response to each. The sensors of the sensor module can take the form of chemically sensitive resistors having resistances that vary according to the identity and concentration of an adjacent vapor. These chemically sensitive resistors can each be connected in series with a reference resistor, between a reference voltage and ground, such that an analog signal is established for each chemically sensitive resistor. The resulting analog signals are supplied to an analog-to-digital converter, to produce corresponding digital signals. These digital signals are appropriately analyzed for vapor identification.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/178,443, filed Oct. 23, 1998, which is acontinuation-in-part of U.S. patent application Ser. No. 09/045,237,filed Mar. 20, 1998. This application is also a continuation-in-part ofU.S. patent application Ser. No. 09/141,847, filed Aug. 27, 1998. Thisapplication farther claims the benefit of U.S. Provisional ApplicationSer. No., entitled “Electronic-Nose Device,” filed Mar. 3, 1999. All ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to the detection and identificationof analytes using a portable sensing apparatus. More particularly, thepresent invention relates to a portable handheld electronic nose(e-nose) device.

[0003] An electronic nose is an instrument used to detect vapors orchemical analytes in gases, solutions, and solids. In certain instances,the electronic nose is used to simulate a mammalian olfactory system. Ingeneral, an electronic nose is a system having an array of sensors thatare used in conjunction with pattern-recognition algorithms. Using thecombination of chemical sensors, which produce a fingerprint of thevapor or gas, the recognition algorithms can identify and/or quantifythe analytes of interest. The electronic nose is thus capable ofrecognizing unknown chemical analytes, odors, and vapors.

[0004] In practice, an electronic nose is presented with a substancesuch as an odor or vapor, and the sensor converts the input of thesubstance into a response, such as an electrical response. The responseis then compared to known responses that have been stored previously. Bycomparing the unique chemical signature of an unknown substance to“signatures” of known substances, the unknown analyte can be determined.A variety of sensors can be used in electronic noses that respond tovarious classes of gases and odors.

[0005] A wide variety of commercial applications are available forelectronic noses including, but not limited to, environmental toxicologyand remediation, biomedicine, such as microorganism classification ordetection, material quality control, food and agricultural productsmonitoring, heavy industrial manufacturing, ambient air monitoring,worker protection, emissions control, and product quality testing. Manyof these applications require a portable device because they are locatedin the field or because they have an inaccessible location for largerlaboratory models. Conventionally, most of the electronic noses havebeen large cumbersome laboratory models incapable of being used in thefield and pilot plant applications. If available, a portable or handhelddevice would provide the portability required for pilot plant and fieldlocations. Unfortunately, the portable chemical detectors that have beendeveloped thus far have many limitations that have kept them from beingwidely accepted.

[0006] For instance, U.S. Pat. No. 5,356,594, which issued to Neel etal., discloses a portable volatile organic monitoring system designedfor use in detecting fugitive emissions. The device includes a bar codereader for inventorying the emission site. The device contains a singlesensor responsive to ionized gas, however the device only detects theamount (i.e., concentration) of the volatile compound. The device isincapable of identifying the volatile organic compound. Thus, the deviceis merely a vapor amount logger and not a portable electronic nose. Assuch, the user is required to know the identity of the vapor beingquantitated or this information must be stored elsewhere.

[0007] Another example of a portable device is disclosed in U.S. Pat.No. 4,818,348 issued to Stetter. Although this portable device is moresophisticated than the previous example, it still has many limitations.In this instance, the device is capable of identifying a gas or vapor,but the applications are quite limited because of sensor architecturallimitations. The sensors making up the array are permanently fixed, andthus, the number and variety of analytes and gases that the device iscapable of identifying is quite small. Moreover, because the analyte orvapor being identified interacts with each sensor of the array in adifferent amount, the reproducibility and stability of the device isquite limited. These limitations effect the device's accuracy inidentifying unknowns.

[0008] In view of the foregoing, there remains a need in the art for anelectronic nose that is portable and, in certain instances, handheld.Moreover, a device is needed that is useful in a broad variety ofapplications and can respond accurately to a broad variety of gases,analytes, and fluids. A vapor-sensing device is needed that is veryversatile, stable, and meets the needs of a wide range of industries andusers. The present invention fulfills these and other needs.

SUMMARY OF THE INVENTION

[0009] The invention relates generally to a sensing apparatus (alsoreferred to as an electronic-nose or e-nose device). The apparatus iscompact and, in certain embodiments, configured to be a handheld device.The e-nose device can be used to measure or identify one or moreanalytes in a medium such as vapor, liquid, gas, solid, and others. Someembodiments of the e-nose device includes at least two sensors (i.e., anarray of sensors) and, in some other embodiments, about two to about 200sensors in an array and preferably about four to about 50 sensors in thearray.

[0010] The e-nose device is versatile and meets the needs of a widerange of applications in various industries. In certain embodiments, thedevice is designed as a slim handheld, portable device with variousfunctionalities. In another embodiments, the device is designed as aportable field tool with full functionality. The e-nose device typicallyincludes an internal processor for processing samples and reportingdata. Optionally, the device can be coupled to a computer, such as apersonal computer, for access to set-up and advanced features and fortransfer of data files.

[0011] In some embodiments, sections of the e-nose device are disposedwithin modules that can be installed, swapped, and replaced asnecessary. For example, the sensor module, sampling wand or nose,battery pack, filter, electronics, and other components, can bemodularized, as described below. This modular design increases utility,enhances performance, reduces cost, and provides additional flexibilityand other benefits.

[0012] A specific embodiment of the invention provides a handheldsensing apparatus that includes a housing, a sensor module, a samplechamber, and an analyzer. The sensor module and the analyzer mount inthe housing. The sensor module includes at least two sensors thatprovide a distinct response to a particular test sample. The samplechamber is defined by the housing or the sensor module, or both, andincorporates an inlet port and an outlet port. The sensors are locatedwithin or adjacent to the sample chamber. The analyzer is configured toanalyze a particular response from the sensors and to identify orquantify, based on the particular response, analytes within the testsample.

[0013] In a variation of the above embodiment, the housing of thehandheld sensing apparatus includes a receptacle, and the sensor moduleis removably mounted in the receptacle of the housing. In thisembodiment, the sensor module can include one or more sensors.

[0014] Another specific embodiment of the invention provides a sensormodule configured for use with a sensing apparatus. The sensor module isdisposed within a housing that defines a receptacle. The sensor moduleincludes a casing, a sample chamber, an inlet port, an outlet port, atleast two sensors, and an electrical connector. The casing is sized andconfigured to be received in the receptacle of the sensing apparatus.The inlet port is configured to be releasably engageable with a portconnection of the sensing apparatus when the sensor module is receivedin the receptacle. The inlet port receives a test sample from thesensing apparatus and directs the test sample to the sample chamber. Theoutlet port is configured to discharge the test sample from the samplechamber. The sensors are located within or adjacent to the samplechamber and are configured to provide a distinct response when exposedto one or more analytes located within the sample chamber. Theelectrical connector is configured to be releasably engageable with amating electrical connector of the sensing apparatus when the sensormodule is received in the receptacle. The electrical connector transmitsthe characteristic signals from the sensors to the sensing apparatus.

[0015] Yet another specific embodiment of the invention provides ahandheld sensing apparatus for measuring the concentration of one ormore analytes within a sample chamber. The sensing apparatus includestwo or more chemically sensitive resistors, conditioning circuitry, ananalog-to-digital converter (ADC), and an analyzer. Each chemicallysensitive resistor has a resistance that varies according to aconcentration of one or more analytes within the sample chamber. Theconditioning circuitry couples to the chemically sensitive resistors andgenerates an analog signal indicative of the resistance of theresistors. The ADC couples to the conditioning circuitry and provides adigital signal in response to the analog signal. The analyzer couples tothe ADC and determines, based on the digital signal, the identity orconcentration of the analyte(s) within the sample chamber.

[0016] Yet another embodiment of the invention provides a portable,handheld vapor sensing apparatus that includes a sensor moduleincorporating a plug-in array of vapor sensors that provide differentelectrical responses to one or more distinct vapors. The apparatusincludes a handheld housing, and the sensor module optionally can beremovably mounted in a receptacle formed in the housing. The sensormodule defines a sample chamber to which the array of vapor sensors isexposed. The sample chamber incorporates a vapor inlet and a vaporoutlet, and a pump is mounted within the housing for directing a vaporsample from the vapor inlet through the sample chamber to the vaporoutlet. A monitoring device also is mounted within the housing, formonitoring the electrical responses of the array of vapor sensors andfor producing a corresponding plurality of sensor signals. In addition,an analyzer is mounted within the housing for analyzing the plurality ofsensor signals and to identify any vapor sample directed through thesample chamber by the pump.

[0017] In more detailed features of the invention, the handheld vaporsensing apparatus further includes a controller or processor configuredto control the pump either to direct one of a plurality of referencevapors or an unknown vapor sample through the sample chamber. When thecontroller is controlling the pump to direct one of the plurality ofreference vapors through the sample chamber, the monitoring devicemonitors the electrical responses of the array of vapor sensors toproduce a reference signature. Thereafter, when the controller iscontrolling the pump to direct the unknown vapor sample through thesample chamber, the monitoring device monitors the electrical responsesof the array of vapor sensors to produce a vapor sample signature. Theanalyzer then compares the vapor sample signature with a plurality ofreference signatures, to identify the unknown vapor sample.

[0018] In other more detailed features of the invention, the samplechamber of the handheld vapor sensing apparatus is defined by the sensormodule, alone, and it is sealed from the external environment except forthe vapor inlet and the vapor outlet. In addition, each sensor moduleincludes a plurality of first electrical connectors and a plurality ofdevices of substantially identical size and shape, the devices togethercarrying the array of vapor sensors and each including a secondelectrical connector along one edge thereof, for mating engagement withone of the first electrical connectors.

[0019] In yet further more detailed features of the invention, thehandheld vapor sensing apparatus further includes an electrical circuitthat controls the temperature of the array of vapor sensors. Inaddition, when the sensor module is configured to be removably mountedin the housing receptacle, the module carries an identifier foridentifying the vapor sensors it carries, and the monitor further isconfigured to read the identifier carried by the sensor module receivedin the receptacle.

[0020] In an embodiment, the sensors are implemented with chemicallysensitive resistors having resistances that vary according to theconcentration of one or more prescribed vapors within the samplechamber. These chemically sensitive resistors are each connected inseries with a separate reference resistor, between a reference voltageand ground, such that an analog signal is established for eachchemically sensitive resistor. An analog-to-digital converter isresponsive to these analog signals and to the reference voltage, toproduce digital output signals indicative of the resistances of thevarious chemically sensitive resistors. A multiplexer can be includedfor sequentially connecting the various analog output signals to theanalog-to-digital converter. In addition, an analyzer is responsive tothe digital output signals, to determine the presence and/orconcentration of one or more prescribed vapors within the samplechamber.

[0021] Other features and advantages of the present invention shouldbecome apparent from the following description of the preferredembodiments, taken in conjunction with the accompanying drawings, whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 shows a pictorial view of an operator using an e-nosedevice of the invention.

[0023]FIGS. 2A and 2B show a top and bottom perspective view,respectively, of an embodiment of an e-nose device.

[0024]FIG. 3A shows six perspective views of an embodiment of anothere-nose device.

[0025]FIG. 3B shows four different embodiments of noses for the e-nosedevice of FIG. 3A.

[0026]FIG. 4 shows a diagram of an embodiment of the subsystems of thee-nose device.

[0027]FIG. 5 shows an exploded perspective view of some of the majorcomponents of the e-nose device of FIG. 2A.

[0028]FIGS. 6A and 6B show an exploded perspective view of twoembodiments of the mechanical subsystem of the e-nose device.

[0029]FIG. 6C shows an exploded perspective view of an embodiment of afilter.

[0030] FIGS. 7A-7B show a perspective view and a top sectional view,respectively, of an embodiment of a sensor module that includes foursensor devices mounted within two sample chambers.

[0031]FIG. 7C shows a perspective view of the sensor array device.

[0032]FIGS. 8A and 8B show a perspective view and a top sectional view,respectively, of an embodiment of another sensor module that includesfour plug-in sensor devices within a single sample chamber.

[0033]FIGS. 9A through 9C show a perspective view, a side sectionalview, and a partial top sectional view, respectively, of an embodimentof a yet another sensor module that includes a single sensor arraydevice.

[0034]FIG. 10 shows various accessories for the e-nose device

[0035]FIG. 11 shows a perspective view of an e-nose device shown mountedvertically in an electrical charging station and coupled to a hostcomputer.

[0036]FIG. 12A shows a diagram of an embodiment of the electricalcircuitry within the e-nose device.

[0037]FIG. 12B shows an embodiment of a voltage divider network used tomeasure the resistance of a chemically sensitive resistor.

[0038]FIG. 12C shows a diagram of another embodiment of the electricalcircuitry within the e-nose device.

[0039]FIGS. 13A through 13G show an embodiment of suitable flowcharts ofthe functional steps performed by the e-nose device in implementing themeasurement and analysis procedures.

[0040]FIG. 14 shows a diagram of an embodiment of the menu selection forthe e-nose device.

[0041]FIG. 15 shows a graph of a principal component analysis of theresponses to a series of esters using the handheld apparatus of thepresent invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0042]FIG. 1 shows a pictorial view-of an operator using an e-nosedevice 100 of the invention. In the embodiment shown in FIG. 1, e-nosedevice 100 is a portable, handheld instrument for sensing the presenceof one or more specified analytes in a particular sample. As use herein,a sample is a unit of a vapor, liquid, solution, gas, solid, or otherforms, and mixtures thereof, of a substance being analyzed. Thus, asample includes chemical analytes, odors, vapors, and others. The samplecan comprise a single analyte or a plurality of analytes. In FIG. 1,e-nose device 100 is used for industrial monitoring and detection, i.e.,to identity and quantify noxious gas escaping from an industrial valveassembly. E-nose device 100 can also be used for many otherapplications, as enumerated below.

[0043]FIG. 2A shows a top perspective view of an embodiment of an e-nosedevice 100 a. E-nose device 100 a includes an elongated housing 110 ahaving a lower end sized to be conveniently grasped and supported by thehand of an operator. A display 120 a and several push-button controlswitches 122 a through 122 c are located on the housing's topside, forconvenient viewing and access by the operator. Push-button switches 122are used to control the device during its various operating modes.Display 120 a displays information about such operating modes and theresults of the device's sensing.

[0044] A tubular sampling wand 130 a and an exhaust port 134 areprovided to respectively receive and discharge samples to be analyzed.The sampling wand is also referred to as a nose or snout. A plug-insensor module 150 a is shown installed in its socket located at the baseof e-nose device 100 a. The operation of sensor module 150 a isdescribed in detail below. An electrical connector 126 located at thelower end of housing 110 a allows for communication with a hostcomputer, and electrical contacts 128 allow for application of externalpower that could be used to operate the e-nose device and to rechargethe rechargeable battery within the e-nose device.

[0045]FIG. 2B shows a bottom perspective view of e-nose device 100 a. Asshown in FIG. 2B, one sampling wand 130 a 1 is secured in place and asecond sampling wand 130 a 2 is being stored in an elongated recess 162located on the underside of device 100 a. Sampling wand 130 a can bestored when not in use and is releasably secured in place by a pair ofspring clips 164 a and 164 b. Plug-in sensor module 150 a is shownremoved from its socket 152.

[0046]FIG. 3A shows six perspective views of an embodiment of anothere-nose device 100 b. E-nose device 100 b includes a nose 130 b, adisplay 120 b, and a set of buttons 124. Similar to e-nose device 10 a,nose 130 b in e-nose device 100 b is removably coupled to a housing 110b. A set of connectors 127 allows for interconnection with externaldevices and systems.

[0047]FIG. 3B shows four different embodiments of noses 130 c through130 f. As these examples illustrate, the noses can be speciallydimensioned for improved performance in specific applications.

[0048]FIG. 4 shows a diagram of an embodiment of the subsystems ofe-nose device 100. The upper half of FIG. 4 shows an electricalsubsystem 410 and the lower half shows a (i.e., substantiallymechanical) subsystem 412 that processes test samples. Within subsystem412, a test sample is received via a nose 430 and provided to a manifold440. Similarly, a reference or background sample is received via anintake port 432 and provided through a filter 436 to manifold 440.Filter 436 can be a blank filter, a carbon filter, or others. Manifold440 directs the test and clean samples to a solenoid 444 that selectsone of the samples as the solenoid output. The selected sample isdirected through manifold 440 to a sensor module 450. Sensor module 450includes at least two sensors that detect analytes in the selectedsample. Sensor module 450 generates a signal (or a “signature”)indicative of the detected analytes and provides this signal toelectrical subsystem 410. The selected sample is then provided fromsensor module 450, through manifold 440, further through a pump 460, andto an exhaust port 434. Nose 430, intake port 432, exhaust port 434, andsensor module 450 in FIG. 4 generally corresponds to nose 130 a, intakeport 132, exhaust port 134, and sensor module 150 a in FIG. 2A,respectively.

[0049]FIG. 4 shows an embodiment of subsystem 412. Many other componentsand devices (not shown) can also be included in subsystem 412. Further,it is not necessary for all of the components and devices shown in FIG.4 to be present to practice the present invention. Moreover, thecomponents and devices may be arranged in different configurations thanthat shown in FIG. 4. For example, pump 460 can be coupled to the outputof solenoid 444 instead of exhaust port 434.

[0050] As shown by the embodiment in FIG. 4, electrical subsystem 410includes a PCB assembly 470 that interconnects with a display 472, abattery pack 474, a keypad 476, an analog port 478, an interface 480,and switches 482 a and 482 b. Display 474 can be a liquid crystaldisplay (LCD) and can include backlight controllers drivers and(optionally) a touchpad. A contrast adjustment mechanism can be providedto adjust display 472. Electrical subsystem 410 is described in furtherdetail below.

[0051]FIG. 5 shows an exploded perspective view of some of the majorcomponents of e-nose device 100 a. FIG. 5 also depicts an embodiment ofa subsystem 412 a. In use, e-nose device 100 a is configured to draw ina test sample (i.e., in a vapor, liquid, or gas medium) from a locationof interest (i.e., the space adjacent to the valve assembly in FIG. 1)through sampling wand 130 a, and to direct this sample through plug-insensor module 150 a installed in socket 152. After passing throughsensor module 150 a, via ports 512 a and 512 b, the sample is directedoutwardly through exhaust port 134 at the side of the device. Atspecified times during the device's various operating modes, a referencesample is drawn into the device via intake port 132, directed throughsensor module 150 a, and discharged through exhaust port 134.

[0052] The device's housing 110 a can be formed of molded plastic andincludes a lower half 112 a and an upper half 112 b. Many of thedevice's internal components are conveniently and efficiently mounted ona printed circuit board (PCB) 510 that extends substantially across thedevice's interior volume. Display 120 a is mounted at the top end of thePCB, where it is visible through an aperture 520 formed in the housing'supper half 112 a. The push-button control switches 122 a through 122 care mounted below display 120 a, in positions where they can extendthrough correspondingly sized openings 522 formed in the housing's upperhalf 112 a.

[0053] A valve assembly 540 mounted on the underside of PCB 510 receivesthe test sample drawn into e-nose device 100 a via sampling wand 130 aand the reference sample via intake port 132. The test sample isdirected from sampling wand 130 a to the valve assembly via a tube 532,and the clean sample is directed from intake port 132 to the valveassembly via a tube 534. Valve assembly 540 is configured to select fromone of two sources, coming via either sampling wand 130 a or intake port132. From valve assembly 540, the sample from the selected source isdirected via a tube 536 through socket 152 to sensor module 150 a, whichis located on the top side of the PCB. After analysis by the sensormodule, the sample is directed through a tube 538 to a pump 560 locatedon the underside of the PCB. Finally, the sample is discharged from thedevice by directing it from pump 560 through a tube 562 to exhaust port134. Alternatively, pump 560 could be located in the path between valveassembly 540 and sensor module 150 a. In an embodiment, the componentscoming in contact with the sample being processed (including tubes 532,534, 536, 538, and 562) are formed of an inert or non-corrosivematerial, such as Teflon, stainless steel, or Teflon-coated metal. Valveassembly 540 in FIG. 5A generally corresponds to manifold 440 andsolenoid 444 in FIG. 4, and pump 560 corresponds to pump 460.

[0054] In certain aspects, the handheld apparatus of the presentinvention includes an optional preconcentrator. Advantageously, withcertain analytes, such as high vapor pressure analytes, the analyte isconcentrated on an absorbent. The preconcentrator can be used toincrease the concentration of analytes in the test sample.Preconcentrators are traps composed of an adsorbent material. In use, anadsorbent material attracts molecules from the gas sample that areconcentrated on the surface of the adsorbent. Subsequently, the sampleis “desorbed” and analyzed. Suitable preconcentrator materials include,but are not limited to, a polymeric adsorbent material, unsilanizedglass wool, Teflon or porus glass fiber, and the like. The adsorbentmaterial is packed in a tube, such as a steel tube.

[0055] During use, the sample is drawn into the trap that concentratesthe components of interest. In some instances, the tube is wrapped witha wire through which current can be applied to heat and thus, desorb thetest sample. The sample is thereafter transferred into the modulecontaining the sensors.

[0056] The preconcentrator can be disposed in various locations betweenthe sampling wand and the sensor module. In certain aspects, thepreconcentrator can be placed in the nozzle of the device or,alternatively, in the manifold or other convenient location upstream ofthe sensor module. For example, the preconcentrator can be disposedwithin valve assembly 540, or housed in a unit coupled to the valveassembly (not shown in FIG. 5). Optionally, additional valves can beinstalled in the device facilitating preconcentration and sensing.

[0057] Suitable commercially available adsorbent materials used inpreconcentrators include, but are not limited to, Tenax TA, Tenax GR,Carbotrap, Carbopack B and C, Carbotrap C, Carboxen, Carbosieve SIII,Porapak, Spherocarb, and combinations thereof. Preferred adsorbentcombinations include, but are not limited to, Tenax GR and Carbopack B;Carbopack B and Carbosieve SIII; and Carbopack C and Carbopack B andCarbosieve SIII or Carboxen 1000. Those skilled in the art will know ofother suitable absorbents.

[0058] Operation of e-nose device 100 is controlled by a processordisposed within an electronic unit 570 mounted on the topside of PCB510. Electronic unit 570 further includes one or more memory devices tostore program codes, data, and other configuration information. Theelectronic unit and control of the e-nose device is described in furtherdetail below.

[0059]FIG. 6A shows an exploded perspective view of an embodiment ofanother subsystem 412 b. Subsystem 412 b includes a manifold 640 amounted on a manifold seal plate 642 a. Manifold 640 a includes fittingsfor mounting a valve (or solenoid) 644 a, fittings for mounting a sensormodule 650 a, and fittings for mounting a pump 660 a. The sample isdirected between the various sub-assemblies (e.g., valve 644 a, sensormodule 650 a, and pump 660 a) via cavities located within manifold 640 aand tubes (not shown). Manifold 640 a further includes a recessedopening 648 a configured to receive a filter 636 a.

[0060]FIG. 6B shows an exploded perspective view of an embodiment of yetanother subsystem 412 c. Subsystem 412 c includes a manifold 640 bmounted on a manifold seal plate 642 b via a seal plate gasket 644 b.Manifold 640 b includes fittings for mounting a valve (or solenoid) 644b and fittings for mounting a pump 660 b. A filter cartridge 646 bmounts on top of manifold 640 b and includes a recessed opening 648 bconfigured to receive a filter element. A filter cover 636 b enclosesrecessed opening 648 b and an O-ring 638 b provides a seal for thefilter. The sample is directed between the various sub-assemblies (e.g.,valve 644 b and pump 660 b) via cavities located within manifold 640 band tubes (not shown).

[0061] Filter 636, manifold 640, valve 644, sensor module 650, and pump660 in FIGS. 6A and 6B correspond to filter 436, manifold 440, solenoid444, sensor module 450, and pump 460 in FIG. 4, respectively.

[0062]FIG. 6C shows an exploded perspective view of an embodiment of afilter. The filter includes a circular base unit 680 having an outerwall 682 and an inner wall 686. A set of small-size openings is disposedwithin outer wall 682 for drawing in samples into the filter. A innercircular ring 684 covers inner wall 686 that has disposed thereinanother set of small size openings, for drawing the samples from thefilter. A filter material (e.g., charcoal) 688 for filtering the samplesis disposed within the space between the outer and inner walls. O-ring638 b is used to seal the filter.

[0063] FIGS. 7A-7B show a perspective view and a top sectional view,respectively, of an embodiment of a sensor module 150 b that includesfour sensor devices mounted within two sample chambers 710 a and 710 b.In FIGS. 7A and 7B, sensor module 150 b is depicted as being configuredfor non-removable securement to the PCB, but which alternatively couldbe configured as a plug-in module such as sensor module 150 a. In aspecific embodiment, sensor module 150 b incorporates four plug-insensor array devices 720, each including eight chemically sensitivesensors 740. Sensor module 150 b can include greater or fewer number ofsensor array devices, and each sensor array device can include greateror fewer number of sensors. The four sensor array devices 720 aremounted vertically in pairs on a board 730. A cover 732 having a pair ofelongated recesses is secured overboard 730 so as to define two separatesample chambers 710 a and 710 b, one for each pair of sensor arraydevices 720. Sensor array devices 720 are of similar shape and size, andeach can be received in any one of the four connectors, or receptacles722, formed in board 730.

[0064]FIG. 7C is a perspective view of one sensor array device 720. Inan embodiment, each sensor array device 720 includes an array of eightchemically sensitive sensors 740, each providing a particularcharacteristic response when exposed to a test sample carrying analytesto be sensed. In an embodiment, the sensors are implemented usingchemically sensitive resistors that provide particular resistances whenexposed to a test sample. A multi-contact electrical connector 742 islocated along the lower edge of sensor array device 720 and isconfigured for insertion into one of four receptacles 722. Suitablesensor arrays of this kind are disclosed in U.S. Pat. No. 5,575,401,issued in the names of Nathan S. Lewis et al., entitled “Sensor Arraysfor Detecting Analytes in Fluids,” and incorporated herein by reference.Those of ordinary skill in the art will appreciate that variousalternative chemically sensitive sensors or devices could also be used.

[0065] As shown in FIG. 7B, the test sample is directed through sensormodule 150 b from an inlet port 750, through two sample chambers 710 aand 710 b, and to an outlet port 760. Sensor array devices 720 arearranged such that the test sample moves laterally across the exposedchemically sensitive sensors. Baffles 762 and 764 are located at therespective leading and trailing ends of each sample chamber, to assistin providing an efficient flow pattern, as shown in FIG. 7B.

[0066]FIGS. 8A and 8B show a perspective view and a top sectional view,respectively, of an embodiment of another sensor module 150 c thatincludes four plug-in sensor devices 820 within a single cavity orsample chamber 810. Sample chamber 810 is defined, in part, by a cover832 that is secured over a board 830. This configuration can be designedto provide a longer dwell time for the test sample within the samplechamber, which can be advantageous in some applications.

[0067] Like the chemically sensitive sensors included on sensor arraydevices 720 in FIGS. 7A and 7B, the chemically sensitive sensorsincluded on sensor array device 820 in FIGS. 8A and 8B can take the formof the arrays disclosed in U.S. Pat. No. 5,575,401. Those of ordinaryskill in the art will appreciate that various alternative chemicallysensitive sensors or devices could also be used.

[0068]FIGS. 9A and 9B show a perspective view and a side sectional view,respectively, of an embodiment of yet another sensor module 150 d thatincludes a single sensor array device 920. In a specific embodiment,sensor array device 920 includes 32 chemically sensitive sensorsarranged in a two-dimensional grid and is mounted in a generallyhorizontal orientation on a socket 922. Of course, sensor array device920 can include greater or fewer number of sensors. A screen 924 (seeFIGS. 9B and 9C) overlays sensor array device 920 and, in an embodiment,includes a separate opening 926 overlaying each chemically sensitivesensor. Screen 924 is attached to a cover 932, the combination of whichdefines an upper chamber 934 and a lower chamber 936. As shown in FIG.9B, the test sample being analyzed is directed from an inlet port 950 toupper chamber 934, and from there through screen 924 to lower chamber936 where it passes across the chemically sensitive sensors. The testsample then exits through an outlet port 960. Again, it will beappreciated that various alternative chemically sensitive sensors anddevices could also be used.

[0069] The e-nose device of the invention includes an array of sensorsand, in certain instances, the sensors as described in U.S. Pat. No.5,571,401 are used. Various sensors suitable for detection of analytesinclude, but are not limited to: surface acoustic wave (SAW) sensors;quartz microbalance sensors; conductive composites; chemiresitors; metaloxide gas sensors, such as tin oxide gas sensors; organic gas sensors;metal oxide field effect transistor (MOSFET); piezoelectric devices;infrared sensors; sintered metal oxide sensors; Pd-gate MOSFET; metalFET structures; metal oxide sensors, such as a Tuguchi gas sensors;phthalocyanine sensors; electrochemical cells; conducting polymersensors; catalytic gas sensors; organic semiconducting gas sensors;solid electrolyte gas sensors; piezoelectric quartz crystal sensors; andLangmuir-Blodgett film sensors.

[0070] In a preferred embodiment, the sensors of the present inventionare disclosed in U.S. Pat. No. 5,571,401, incorporated herein byreference. Briefly, the sensors described therein are conductingmaterials and nonconducting materials arranged in a matrix of conductingand nonconducting regions. The nonconductive material can be anonconducting polymer such as polystyrene. The conductive material canbe a conducting polymer, carbon black, an inorganic conductor and thelike. The sensor arrays comprise at least two sensors, typically about32 sensors, and in certain instances 1000 sensors. The array of sensorscan be formed on an integrated circuit using semiconductor technologymethods, an example of which is disclosed in PCT Patent Application Ser.No. WO99/08105, entitled “Techniques and Systems for Analyte Detection,”published Feb. 19, 1999, and incorporate herein by reference.

[0071] In certain instances, the handheld device of the presentinvention comprises an array of surface acoustic wave (SAW) sensors,preferably polymer-coated SAW sensors. The SAW device contains up to sixand typically about four sensors in the array. Optionally, the deviceincludes a preconcentrator with a heater for desorption of the sample.

[0072] As will be apparent to those of skill in the art, the sensorsmaking up the array of the present invention can be made up of varioussensor types as set forth above. For instance, the sensor array cancomprise a conducting/nonconducting regions sensor, a SAW sensor, ametal oxide gas sensor, a conducting polymer sensor, a Langmuir-Blodgettfilm sensor, and combinations thereof.

[0073]FIG. 10 shows various accessories for the e-nose device. A case1010 is provided for easy transport of the e-nose device and itsaccessories. A power cord 1012 and a car cord 1014 can eachinterconnects the e-nose device to a power source (i.e., a wall socketor car lighter) for recharging a rechargeable battery within the e-nosedevice. These cords also allow for operation of the e-nose devicewithout the battery. A bracket or stand 1016 holds the e-nose device inthe desired position. A (primary or spare) battery 1018 allows thee-nose device to be used without connection to a power source. A serialcable 1020 and an analog cable 1022 are used to interconnect the e-nosedevice with a personal computer and other test equipment. A stylus 1024is provided for use with a touchscreen. One or more snouts 1030 can alsobe provided as spares or for use in a particular set of applications. Asample syringe 1032 can be used for collection of test samples.

[0074]FIG. 11 is a perspective view of e-nose device 100 shown mountedvertically in an electrical charging station 1108 and coupled to a hostcomputer 1110. Charging station 1108 recharges the rechargeable batteryof e-nose device 100 via electrical contacts 128 (see FIGS. 2A and 2B).E-nose device 100 is also depicted being coupled to host computer 1110via a data line 1120. Host computer 1110 can be used to update e-nosedevice 100 with various information such as the identity of varioustarget vapors to which the device is to be exposed, as well as toretrieve information from the device such as the results of the device'ssample analyses.

[0075]FIG. 12A is a diagram of an embodiment of the electrical circuitrywithin e-nose device 100. In an embodiment, the electrical circuitrymeasures he resistances of the arrays of chemically sensitive resistorsmounted on the sensor array devices (see FIGS. 7 through 9) andprocesses those measurements to identify and quantify the test sample.The circuitry is mounted, in part, on the PCB and includes a processor1210, a volatile memory (designated as a RAM) 1212, a non-volatilememory (designated as ROM) 1214, and a clock circuit 1216. In theembodiment in which plug-in sensor module 150 a is used (see FIGS. 2Aand 5), the chemically sensitive resistors are coupled to the electricalcircuitry via mating electrical connectors 552 a and 552 b (see FIG. 5)that are engaged when sensor module 150 a is plugged into e-nose device100 a.

[0076] The chemically sensitive resistors used to implement the sensorstypically have baseline resistance values of greater than 1 kilo-ohm(KΩ). These baseline values can vary as much as ±50% over time. Forexample, a particular chemically sensitive resistor may have a baselineresistance that varies between 15 KΩ and 45 KΩ. This large resistancevariability imposes a challenge on the design of the resistancemeasurement circuitry. In addition, the ratio of the change inresistance to the initial baseline resistance, or ΔR/R, which isindicative of the concentration of the analytes, can be very small(i.e., on the order of hundreds of parts per million, or 0.01%). Thissmall amount of change, likewise, imposes a challenge on the design ofthe measurement circuitry. Further, some sensor module embodimentsinclude multiple (e.g., 32) chemically sensitive resistors, and it isdesirable to measure the resistance values of all resistors with minimumcircuit complexity.

[0077]FIG. 12B shows an embodiment of a voltage divider network used tomeasure the resistance of a chemically sensitive resistor 1220.Chemically sensitive resistor (Rch) 1220 is coupled in series to areference resistor (Rrei) 1222 to form a voltage divider network. In anembodiment, a number of voltage divider networks are formed, one networkfor each chemically sensitive resistor, with each network including achemically sensitive resistor coupled in series to a correspondingreference resistor. The reference resistors are selected to have arelatively low temperature coefficient. In an alternative embodiment, asingle reference resistor is coupled to all chemically sensitiveresistors.

[0078] Referring back to FIG. 12A, a power supply 1224 supplies apredetermined reference voltage (Vref) to the voltage divider networkssuch that small changes in the resistance value of each chemicallysensitive resistor cause detectable changes in the network outputvoltage. By appropriately selecting the values of the referenceresistors, the electrical current through each chemically sensitiveresistor can be limited, for example, to less than about 25 microamperes (μA). This small amount of current reduces the amount of 1/ƒnoise and improves performance.

[0079] The analog voltages from the resistor divider networks areprovided through a multiplexer (MUX) 1226 to an analog-to-digitalconverter (ADC) 1230. MUX 1226 selects, in sequence, the chemicallysensitive resistors on the sensor module. Optionally, a low-noiseinstrumentation amplifier 1228 can be used to amplify the voltage priorto digitization, to improve the ADC's performance and provide increasedresolution.

[0080] In an embodiment, ADC 1230 is a 22-bit (or higher) delta-sigmaADC having a wide dynamic range. This allows low-noise amplifier 1228 tobe set to a fixed gain (i.e., using a single high precision resistor).Commercially available low cost delta-sigma ADCs can reach samplingspeeds as fast as about 1 millisecond per channel.

[0081] In one implementation, the reference voltage provided by powersupply 1224 to the voltage divider networks is also provided to areference input of ADC 1230. Internally, ADC 1230 compares the dividernetwork output voltages to this reference voltage and generatesdigitized samples. With this scheme, adverse effects on the dividernetwork output voltages due to variations in the reference voltage aresubstantially reduced.

[0082] The digitized samples from ADC 1230 are provided to processor1210 for further processing. Processor 1210 also provides timing signalsto MUX 1226 and ADC 1230. Timing for the data acquisition can also beprovided via a serial link to the ADC and via select lines of the MUX.

[0083]FIG. 12C is a diagram of another embodiment of the electricalcircuitry within e-nose device 100. In FIG. 12C, four 8-channelmultiplexers (MUXes) 1256 a through 1256 d are provided for addedflexibility. The inputs of MUXes 1256 couple to the voltage dividernetworks (not shown) and the outputs of MUXes 1256 a through 1256 bcouple to four amplifiers 1258 a through 1258 d, respectively. Theselect lines for MUXes 1256 are processor controlled. The use ofexternal MUXes offer a low ON resistance and fast switching times. Theoutputs of amplifiers 1258 couple to four inputs of an ADC 1260.

[0084] Each amplifier 1258 is a differential amplifier having areference (i.e., inverting) input that couples to a digital-to-analogconverter (DAC) 1262. The DC offset of the amplifier is controlled byprocessor 1250 by measuring the offset with ADC 1260 and directing DAC1262 to provide a proper offset correction voltage. To account for DCdrift (i.e., drift in the baseline resistance of the chemicallysensitive resistor) the offset can be adjusted prior to actualmeasurement. Further electrical stability is maintained by placing ADC1260 on-board and using differential MUXes.

[0085] In the embodiments in FIGS. 12A and 12C, amplification is usedwith the voltage divider networks to achieve detection of PPM changes inresistance values. It can be shown that a gain of 50 provides detectionof single PPM increments. In FIG. 12C, amplifiers 1258 also match thesignal to be sampled with the full-scale input of ADC 1260. Thismatching is accomplished by subtracting out the DC component (using DAC1262) and amplifying the AC component. Thus, it is possible to detectsingle PPM changes even with a baseline resistance that varies by ±50%.

[0086] In FIGS. 12A and 12C, the ADCs used to measure the resistancevalues can be implemented using a (i.e., 4-channel) high-resolutiondelta-sigma ADC. The delta-sigma ADC's high resolution coupled with theabove-described sensor biasing scheme(s) deliver high flexibility andprecision. Presently available delta-sigma ADC can provide 20 bits ormore of effective resolution at 10 Hz and 16 bits of resolution at 1000Hz, with power consumption as low as 1.4 mW.

[0087] In an embodiment, the delta-sigma ADC includes differentialinputs, programmable amplifiers, on-chip calibration, and serialperipheral interface (SPI) compatibility. In an embodiment, the ADCinternal differential MUXes are configured: (1) with respect to groundfor increased effective resolution of the measurement, and (2)configured with respect to the reference voltage for high precisionmeasurement, enhanced electronic stability, and to provide a ratiometricmeasuring mechanism. A status signal from the ADC indicates when theinternal digital filter has settled, thus providing an indication toselect the next analog channel for digitization.

[0088] In FIGS. 12A and 12C, processors 1210 and 1260 can be implementedas an application specific integrated circuit (ASIC), a digital signalprocessor (DSP), a controller, a microprocessor, or other circuitsdesigned to perform the functions described herein.

[0089] One or more memory devices are provided to store program codes,data, and other configuration information, and are mounted adjacent tothe processor. Suitable memory devices include a random-access memory(RAM), a dynamic RAM (DRAM), a FLASH memory, a read only memory (ROM), aprogrammable read only memory (PROM), an electrically programmable ROM(EPROM), an electrically erasable and programmable PROM (EEPROM), andother memory technologies. The size of the memories is applicationdependent, and can be readily expanded as needed.

[0090] In an embodiment, the processor executes program codes thatcoordinate various operations of the e-nose device. The program codesinclude interaction software that assists the user in selecting theoperating modes and methods and to initiate the tests. After the e-nosedevice performs a test or operation, the user is optionally presentedwith concise results. In the embodiment in which the device includes aprocessor and a built-in algorithm, complex functions and capabilitiescan be provided by the device. In other embodiments in which simplifiedelectronics is provided, complex functions and capabilities of thee-nose device are optionally set up and driven from a host computerusing PC based software.

[0091] The processors can also be used to provide temperature controlfor each individual sensor array device in the sensor module. In animplementation, each sensor array device can include a back-side heater.Further, the processor can control the temperature of the samplechambers (e.g., chambers 710 a and 710 b in FIG. 7A) either by heatingor cooling using a suitable thermoelectric device (not shown).

[0092] After the processor has collected data representing a set ofvariable resistance measurements for a particular unknown test sample,it proceeds to correlate that data with data representing a set ofpreviously collected standards stored in memory (i.e., either RAM 1212or ROM 1214). This comparison facilitates identification of analytespresent in the sample chamber and determination of the quantity orconcentration of such analytes, as well as detection of temporal changesin such identities and quantities. Various analyses suitable foridentifying analytes and quantifying concentration include principalcomponent analysis, Fischer linear analysis, neural networks, geneticalgorithms, fuzzy logic, pattern recognition, and other algorithms.After analysis is completed, the resulting information is displayed ondisplay 120 or transmitted to a host computer via interface 1232, orboth.

[0093] The identification of analytes and the determination of sampleconcentration can be performed by an “analyzer.” As used herein, theanalyzer can be a processor (such as processors 1210 and 1260 describedabove), a DSP processor, a specially designed ASIC, or other circuitsdesigned to performed the analysis functions described herein. Theanalyzer can also be a general-purpose processor executing program codeswritten to perform the required analysis functions.

[0094] As noted above, to facilitate identification of specifiedanalytes, the variable resistance data from the sensors for a particularunknown test sample can be correlated with a set of previously collectedstandards stored in memory. These standards can be collected using oneof at least two suitable techniques, as described below.

[0095] In one technique, a known reference sample is provided to thesample chamber(s). The known sample can be supplied from a smallreference cartridge (i.e., located within the e-nose device). Thesupplies of this reference sample to the sample chambers can becontrolled by a compact solenoid valve under the control of theprocessor. An advantage of using a known reference sample is the abilityto control the identity of the reference sample. The cartridge can bereplaced periodically.

[0096] In another technique, the unknown test sample supplied to thesample chambers can be selectively “scrubbed” by diverting it through acleansing agent (e.g., charcoal). Again, the diversion of the testsample through the cleansing agent can be controlled by the processorvia a compact solenoid valve. An advantage of this variation is that acartridge is not needed. The cleansing agent can be cleanedperiodically, although it may be difficult to ensure that the referencesample is free of all contaminants.

[0097] The processors in FIGS. 12A and 12C direct data acquisition,perform digital signal processing, and provide control over serialperipheral devices (via SPI), I/O devices, serial communications (viaSCI), and other peripheral devices. Serial peripheral devices that canbe controlled by the processors include the ADC and DAC, a 32K externalEPROM (with the capability to expand to 64K), a 32K RAM with integratedreal time clock and battery back up, a 2×8-character dot matrix display,and others. I/Os that can be controlled include five separatetemperature probes (four are amplified through amplifiers and are usedfor four independent heater control loops utilizing transistors), ahumidity probe, two push buttons, a green LED, and others. Serialcommunications to external devices is provided by the on-board low powerRS-232 serial driver.

[0098] The processors further control the peripheral devices such as thedisplay, the valve assembly, and the pump. The processors also monitorthe input devices (e.g., push button switches 122 in FIG. 2A) andfurther provides digital communication to a host computer via aninterface (e.g., the RS-232 driver) located in the device's housing(e.g., electrical connector 126 in FIG. 2A).

[0099] In the embodiment in FIG. 12C, data acquisition includescommunication and/or control over the (i.e., 20 bit) delta-sigma ADC,the 4-channel (i.e., 12-bit) DAC 1262, and the four discrete 8-channelhigh-speed analog MUXes 1256.

[0100] The on-board memory (i.e., external RAM) is provided for datalogging purposes. In an embodiment, the memory is organized in blocks of32K×8 bits. In an embodiment, each sample from the ADC is 24 bits andoccupies three bytes of memory. Thus, each 32K-byte memory blockprovides storage for 10,666 samples. If all 32 channels are used fordata logging purposes, the memory block provides storage for 333 datapoints/channel. An internal power supply preserves the data stored inthe memory and is designed with a lifetime of over five years. The ADCsampling rate is programmable and the data can be downloaded over thedigital RS-232 interface to the host computer.

[0101] Communication between the on-board processor and the hostcomputer is available to configure the device and to download data, inreal time or at a later time via the RS-232 interface. A transfer rateof 9600 bits/second can transmit approximately 400 data points/second,and higher transfer rates can be used.

[0102]FIGS. 13A through 13G depict an embodiment of suitable flowchartsof the functional steps performed by the e-nose device in implementingthe measurement and analysis procedures outlined generally above. Theseflowcharts show how the e-nose device is initialized and then controlledthrough its various operating modes. In an embodiment, these operatingmodes include: 1) a Target mode, in which the device is calibrated byexposing it to samples of known identity, 2) an Identify mode, in whichthe device is exposed to a samples of unknown identity, and 3) a Purgemode, in which the device is purged of resident samples.

[0103]FIG. 13A shows a flow diagram of an embodiment of the main programmenu of the e-nose device. Initially, the e-nose device's variouselectronic elements (i.e., the display and various internal dataregisters) are initialized or reset, at a step 1312. A functionbackground subroutine is then executed, at a step 1314. This subroutineis further described in FIG. 13B.

[0104] After executing the function background subroutine, the programproceeds to a step 1316 in which the processor determines whether or notpush-button switch B1 (e.g., switch 122 a in FIG. 2A) is being pressed.If it is, the program proceeds to a step 1318 in which the device'soperating mode increments to the next succeeding mode (i.e., from theTarget mode to the Identify mode). Thereafter, the program returns tostep 1314 and re-executes the function background subroutine. Theincrementing of the device's operating mode continues until it isdetermined in step 1316 that switch B1 is no longer being pressed.

[0105] If it is determined at step 1316 that push button B1 is not (orno longer) being pressed, the program proceeds to a step 1320 in whichit is determined whether or not push-button switch B2 (e.g., switch 122b in FIG. 2A) is being pressed. If switch B2 is not being pressed, theprogram returns via an idle loop 1322 to step 1314 and re-executes thefunction background subroutine. Otherwise, if it is determined at step1320 that push-button switch B2 is being pressed, the program proceedsto implement the selected operating mode. This is accomplished by theflowchart depicted in FIG. 13C. FIG. 13B shows a flow diagram of anembodiment of the function background subroutine (step 1314). At a step1330, signals indicative of the measurements and parameters selected bythe user (i.e., the temperature and humidity within the sample chambersof the sensor module) are read from the ADCs configured to detect theinput devices (also referred to as the internal ADCs). The status of thepush-button switches (e.g., switches 122 a through 122 c FIG. 2A) aredetermined, at a step 1332, based on the signals from the internal ADCs.The signals controlling the heaters located on various sensor arraydevices of the sensor module are then updated, at a step 1334. Signalsindicative of the measurements of the divider networks, formed by thechemically sensitive resistors and their corresponding referenceresistors, are read from the instrumentation ADCs (also referred to asthe external ADCs), at a step 1336. Finally, at a step 1338, theprocessor processes any commands received from the host computer via theserial data line. Such commands can include, for example, programminginformation about the identity of various reference samples to besupplied to the e-nose device during the target operating mode. Thefunction background subroutine then terminates.

[0106]FIG. 13C shows a flow diagram of an embodiment of a subroutine fordetermining which one of the operating modes to implement. At a step1340, a determination is made whether or not the-selected operating modeis the Target mode. If it is not, a determination is made whether or notthe selected operating mode is the Identify mode, at a step 1342.Typically, the Identify mode is selected only after the target modesubroutine has been implemented for all of the designated targetsamples. If the selected operating mode is the Identify mode, theprogram executes the identify mode subroutine (depicted in FIG. 13E), ata step 1344.

[0107] Otherwise, if the selected operating mode is not the Identifymode, a determination is made whether or not the selected operating modeis the Purge mode, at a step 1346. If it is, the program executes thepurge mode subroutine (depicted in FIG. 13F), at a step 1348. Otherwise,the program executes the purge target mode subroutine (depicted in FIG.13G), at a step 1350. The purge target mode is the default mode.

[0108] Back at step 1340, if it is determined that the selectedoperating mode is the Target mode, the program proceeds to a step 1352in which the function background subroutine is executed. This providesupdated values for the internal and external ADCs, as described above.Thereafter, at a step 1354, it is determined whether or not push-buttonswitches B1 and B2 are being pressed concurrently. If they are, theprogram does not implement the Target mode and instead returns to theidle loop (step 1322 in FIG. 13A).

[0109] Otherwise, if it is determined at step 1354 that both push-buttonswitches B1 and B2 are not being pressed concurrently, the programproceeds to a step 1356 in which it is determined whether or not switchB1 has been pressed. If it has been, the program proceeds to a step 1358in which the particular target number is incremented. In an embodiment,the e-nose device is configured to measure multiple (e.g., eight)different target samples, and step 1358 enables the operator to selectthe particular target sample that is to be drawn into the device formeasurement. The identity of these target samples previously has beenloaded into the device from the host computer. Thereafter, the programreturns to the step 1352 to execute the function background subroutine.Each time it is determined that switch B1 has been pressed, the programcycles through this loop, incrementing through the preloaded complementof target samples.

[0110] If it is determined at step 1356 that switch B1 has not beenpressed, the program proceeds to a step 1360 in which it is determinedwhether or not switch B2 has been pressed. If it has not, the programreturns to step 1352 to execute the function background subroutine.Otherwise, if it is determined in step 1360 that switch B2 has just beenpressed, the program proceeds to implement the target mode subroutine(depicted in FIG. 13D), at a step 1362.

[0111]FIG. 13D shows a flow diagram of an embodiment of the target modesubroutine. At a step 1370, the most recently updated set ofmeasurements from the external ADC is retrieved. These measurementsrepresent the baseline resistance values of the 32 chemically sensitiveresistors of the sensor module. Next, the pump is conditioned to drawthe designated target sample into the sensor module's sample chamber(s),at a step 1372. A new set of measurements is then retrieved from theexternal ADC, at a step 1374. This new set of measurements indicates theresistance values of the 32 chemically sensitive resistors as theyrespond to the target sample that has been drawn in the samplechamber(s).

[0112] At a step 1376, the 32 resistance measurements (i.e., the“response vector”) for this particular target vapor are normalized. Inan embodiment, this normalization set the sum of all 32 measurementsequal to a value of 1×10⁶. The normalized response vector for His targetsample then is stored in memory, at a step 1378. Finally, at a step1380, the pump and valve assembly are configured to draw clean air intothe sample chamber(s). The target mode subroutine then terminates, andthe program returns to the idle loop (step 1322 in FIG. 13A).

[0113]FIG. 13E shows a flow diagram of an embodiment of the identifymode subroutine. Steps 1390, 1392, 1394, and 1396 in FIG. 13E aresimilar to steps 1370, 1372, 1374, and 1376 in FIG. 13D, respectively.At a step 1398, the normalized response vector for the unknown samplecalculated in step 1396 is compared with the normalize response vectorsfor the various target samples, as determined by earlier passes throughthe target mode subroutine (FIG. 13D) and stored in memory.Specifically, differences between the respective normalized responsevectors are calculated at step 1398, and the smallest difference vectoris determined (i.e., using a least mean square analysis), at a step13100. Also at step 13100, the result of that determination is displayedon a display. Finally, at a step 13102, the pump and valve assembly areconditioned to draw clean air to the sample chamber(s). The identifymode subroutine then terminates, and the program returns to the idleloop (step 1322 in FIG. 13A).

[0114]FIG. 13F shows a flow diagram of an embodiment of the purge modesubroutine. At a step 13120, the pump and valve assembly are conditionedto draw clean air into the sample chamber(s) via the intake port. Theprogram then returns to the idle loop (step 1322 of FIG. 13A).

[0115]FIG. 13G shows a flow diagram of an embodiment of the purge targetmode subroutine. At a step 13130, all of the target sample informationstored in memory is erased. The program then returns to the idle loop(step 1322 in FIG. 13A).

[0116]FIG. 14 shows a diagram of an embodiment of the menu selection forthe e-nose device. In FIG. 14, a main menu 1408 displays the measurementmodes available for the particular e-nose device. The available modescan be dependent, for example, on the particular modules installed inthe e-nose device. In an embodiment, the following modes are availablein the main menu: Identify, Quantify (Qu), Process Control (PC), DataLogging (DL), Train, and Diagnoses. Upon making a mode selection in menuscreen 1408, a menu screen 1410 appears that queries the user to selecta particular method from among a set of available methods.

[0117] By selecting the ID Method option, a menu screen 1412 appearsthat queries the user to press “sniff” to begin identification or“cancel” to return to the main menu. Upon selecting the sniff option,the e-nose device begins the identification process, as shown in a menuscreen 1414, and provides the results upon completion of the process, asshown in a menu screen 1416. The user is provided with an option to savethe results.

[0118] By selecting the Qu Method option, a menu screen 1420 appearsthat queries the user to select a target. If the identity of the targetis unknown, a menu screen 1422 provides the user with the option ofperforming a sniff to identify the unknown target. Upon selecting thesniff option, the e-nose device begins the identification process, asshown in a menu screen 1424, and provides the identity upon completionof the process, as shown in a menu screen 1426. Once the sample isidentified or if the identity is known initially, the target can bequantified in menu screens 1426 and 1428. The e-nose device begins thequantification process, as shown in a menu screen 1430, and provides theresults upon completion of the process, as shown in a menu screen 1432.

[0119] By selecting the PC Method option, a menu screen 1440 appearsthat queries the user to press “sniff” to begin the process control or“cancel” to return to the main menu. Upon selecting the sniff option,the e-nose device begins the process control, as shown in a menu screen1442, and provides the status report, as shown in a menu screen 1444.

[0120] By selecting the DL Method option, a menu screen 1450 appearsthat queries the user to press “sniff” to begin the data logging or“cancel” to return to the main menu. Upon selecting the sniff option,the e-nose device begins the data logging process, as shown in a menuscreen 1452, and provides the status report, as shown in a menu screen1454.

[0121] By selecting the Train option, a menu screen 1460 appears thatqueries the user to select one of a number of training methods. The userselects a particular method and a menu screen 1462 appears that queriesthe user to select one of a number of targets. The user selects aparticular target and a menu screen 1464 appears that queries the userto press “sniff” to begin the training. Upon selecting the sniff option,the e-nose device begins the training process using the method andtarget selected by the user, as shown in a menu screen 1466.

[0122] By selecting the Diagnostics option, a menu screen 1470 appearsthat queries the user to select a diagnostic to run. Possiblediagnostics include, for example, RS-232 port, USB port, sensor rangetest, memory, processor, and program check sum. The user selects aparticular diagnostic and the e-nose device begins the selecteddiagnostic test, as shown in a menu screen 1472, and provides thediagnostic results, as shown in a menu screen 1474.

[0123] Modular Design

[0124] In certain aspects of the invention, the e-nose device isdesigned using modular sections. For example, the nose, filter,manifold, sensor module, power pack, processor, memory, and others canoptionally be disposed within a module that can be installed or swapped,as necessary. The modular design provides many advantages, some of whichare related to the following characteristics: exchangeable, removable,replaceable, upgradable, and non-static.

[0125] With a modular design, the e-nose device can be designed for usein wide variety of applications in various industries. For example,multiple sensor modules, filters, and so on, can be added as the list ofsamples to be measured expands.

[0126] In certain embodiments, the modular design can also provideimproved performance. The various modules (i.e., nose, filter, manifold,sensor module, and so on) can be designed to provide accuratemeasurement of a particular set of test samples. Different modules canbe used to measure different samples. Thus, performance is notsacrificed by the use of a small portable e-nose device. For example, tosense high molecular weight analytes, a certain particular nose chip isplugged in. Then, to analyze lower molecular weight analytes, anothernose chip may be plugged in.

[0127] The modular design can also result in a cost effective e-nosedesign. Since some of the components can be easily replace, it is nolonger necessary to dispose the entire e-nose device if a particularcomponent wears out. Only the failed components are replaced.

[0128] In certain embodiments, the modular design can also provide anupgradable design. For example, the processor and memory module(individually or in combination) can be disposed within an electronicunit that can be upgraded with new technologies, or as required by onthe particular application. Additional memory can be provided to storemore data, by simply swapping out memory modules. Also, the analysisalgorithms can be included in a program module that inserts into thee-nose device. The program modules can then be swapped as desired.

[0129] The modular design can also provide for disposable modules. Thismay be advantageous, for example, when analyzing toxic samples.

[0130] Nose

[0131] In the embodiments described above, the e-nose device includes anexternal sampling wand (or nose or snout). The nose can be attached tothe device using a mechanical interconnect, such as a simple ¼-turntype, a threaded screw, a snap-on mechanical arrangement, and otherinterconnect mechanisms. Many materials can be used to fabricate thenose component, such as injection moldable materials.

[0132] In certain embodiments, the nose is interchangeable and uses astandard luer interconnection. The nose can be, for example, about 1inch to about 50 inches in length and, preferably, the nose is about 6inches to about 20 inches in length. The nose can optionally be ridged,or be a long flexi-hose or a flexible snorkel. In some embodiments, thenose has a luer needle on the smelling end. Optionally, the nose canwithstand an internalized pressure and is joined with a pressured valve.

[0133] As shown in FIG. 3B, the nose can be dimensioned in various sizesand shapes. For example, nose 130 d includes a wide opening that may beadvantageous, for example, when sampling a gas. In contrast, nose 130 fincludes a pointed tip that is more suited for sampling at a specificsite.

[0134] In some alternative embodiments, intake ports (such as intakeport 132) can be used to receive test samples. The intake ports cansubstitute for, or supplement the external nose.

[0135] Sensor Modules

[0136] In certain aspects, the chemically sensitive sensors in thesensor module can be tailored to be particularly sensitive to particularclasses of vapors. For example, the array for one such module canincorporate vapor sensors suitable for differentiating polar analytessuch as water, alcohol, and ketones. Examples of polar polymers suitablefor use as such vapor sensors include poly (4-vinyl phenol) and poly(4-vinyl pyrrolidone).

[0137] The sensor module can optionally be identified by means of anidentification resistor (not shown) having a selected resistance. Thus,prior to processing the variable resistance measurements collected forthe chemically sensitive resistors of each such sensor module, theprocessor measures the resistance of the identification resistor. Inthis manner, the nature of the module's chemically sensitive resistorscan be initially ascertained.

[0138] A mechanism for detection of analytes is disclosed in theaforementioned PCT Patent Application Ser. No. WO99/08105.

[0139] Display

[0140] In some embodiments, the display is a liquid-crystal display(LCD). In other embodiments, the display is a graphical LCD that allowsthe device to display text and graphics. This type of display provides aquality product interaction experience. Examples of LCD modules includethose manufactured by Epson Corporation, such as the EPSON EG7502 (TCMAO822) having a screen size of 57.56 mm by 35.99 mm, a 320×200resolution with 0.8 dot pitch, and transflective and LED edge backlight. Various other LCD modules are also suitable. Preferred LCDmodules offer one or more of the following features: (1) higherresolution to allow for a smaller but comfortable display viewing areas(320×200 and fine dot pitch), (2) low power consumption (e.g., 3 mW to 9mW), (3) multi-line scanning-(active addressing) technology, (4)integrated “touch” panel, (5) integrated power supply and controllerchips, (6) LED backlighting—for smaller module, (6) displays used withvideo, and other features.

[0141] Input Devices

[0142] In certain embodiments, the e-nose device optionally includesinput devices, such as push buttons, a keypad, a keyboard, atouchscreen, switches, other input mechanisms, or a combination of theabove. The keypad can be fabricated from various materials. In certainembodiments, the keypad is molded from silicone rubber, whichadvantageously provides tactile feedback for gloved hands. Moreover,navigational controls can optionally be incorporated into the keypad andbuttons. For example, a “sniff” button can be optionally positioned intothe keypad.

[0143] The keypad can optionally be a membrane type keypad. In thisimplementation, the keypad is formed from laminated sheets of acrylic,Mylar, PC, or other suitable materials. Snap domes can be used toachieve greater tactile feedback for the user. Product graphics can beincorporated into the keypad. Advantageously, the keypad has flexibilitywith graphics, is easy to clean, and has protection from spillage. Inaddition, the keypad is configured with low stroke distances. In certainother instances, a micro-switch, such as for a “sniff” button, is usedto further accentuate the tactile “click” feedback and generate alow-level audible signal.

[0144] In certain embodiments, the e-nose device optionally includes apointer. Advantageously, the pointer provides greater applicationflexibility and ease of use in the field. In certain aspects, thepointer can be used for bar code reading and easy inventory control.Further, the device optionally includes a pad. The pad allows forapplication flexibility, such as in field, training, or lab use.

[0145] The e-nose device optionally includes other input devices, suchas a touch screen. Suitable touch screens include the analog resistivetype. Other touch screens include those similar to the ones in PDA, GPS,and other products. Yet other touch screens include electromagneticresonance types optionally having a dedicated stylus, such as abattery-less stylus. In addition, touch screens can include, but are notlimited to, electrostatic, GSAW, and analog resistive and capacitivetypes. The analog resistive touch screen is preferred since high and lowresolutions can readily be achieved.

[0146] In certain embodiments, the e-nose device notifies the user byproviding general and specific information about the device's currentmode. Operators of the device can see what options are available.Guidelines and instructions are available to assist the users interactwith the product. In certain instances, the descriptions andinstructions are brief and specific. Graphics and icons assist usersthrough the product interaction. Users are provided with a mechanism tostop the device when necessary, and to return to previous screens whereappropriate. These various features collaborate to provide deviceinteractions that are quick, simple, and reliable.

[0147] In other embodiments, the e-nose device provides the users withinformation regarding the status of the device. Examples include, butare not limited to, initiating an action, performing an operation,waiting for input, and so on. Moreover, other device input and outputparameters, such as hardware controls, include, but are not limited to:Scroll Up—keypad; (2) Scroll Down—keypad; (3) Select—keypad; (4)Cancel—keypad; (5) Sniff—keypad; (6) Power-on/Backlight on/off; (7)Digital Input—connector; (8) Analog Output—connector; (9) Serial out(RS232)—RJ11; (10) USB—Standard A; (11) Display contrast—(thumbwheel,analog pot); (12) System reset—pin hole; (13) Battery recharge—jack;(14) pneumatics ports; (15) nose inhale port (sample sniff port); (16)exhale (exhaust); and (17) reference intake.

[0148] Power Pack

[0149] The e-nose device optionally includes a power pack, such as abattery, for providing electrical power. In certain embodiments, thedevice operates from power supply voltages of approximately 3.3 voltsand approximately 5.0 volts DC. In a specific embodiment, the deviceconsumes approximately 3.2 watts or less, with a typical average powerconsumption of approximately 1.8 watts. In an embodiment, the device iscapable of operation from about 1 hour to about 20 hours withoutrequiring a recharge of the power pack.

[0150] The power pack can be fabricated using nickel cadmium (NiCd),nickel-metal hydride (NiMH), lithium ion (Li-ion), sealed lead-acid(SLA), or other battery technologies. Preferably, the battery pack haslow weight and a high power density to keep the volume of the batterysmall. Lithium-ion cells have a relatively high internal resistance andwider range of voltages during a discharge compared to other batterychemistries. A voltage regulator can be used to provide proper voltagesfor the circuitry within the e-nose device. For efficiency, a switchingvoltage regulator can be used in place of linear type regulators. Thevoltage regulator can also be used to provide multiple output voltagesfor different circuitry within the e-nose device. In certain instances,output voltages required from the power supply include values above andbelow the battery voltage. In these instances, a SEPIC topology for theswitching regulator can optionally be used. Conversion efficiency ofsuch switching regulators is approximately 85%. To provide approximately18 watt-hours of energy to the load using such switching regulator, theenergy requirement from the lithium-ion battery pack is approximately 21watt-hours.

[0151] In a specific embodiment, a lithium-ion (Li-ion) battery pack ofapproximately 100 cubic centimeters (cc) in volume and about 250 gramsin weight can optionally be used for the e-nose device. In anotherspecific embodiment, a nickel-metal hydride (NiMH) battery pack can beused that weighs about 370 grams and has a volume of about 150 cc. Otherbatteries capable of providing an equivalent amount of energy include,but are not limited to, a nickel-cadmium (NiCd) battery pack ofapproximately 560 grams and 210 cc and a sealed lead-acid (SLA) batterypack of approximately 750 grams and 350 cc.

[0152] In general, charging times increase and the available batterycapacity reduces for low (e.g., 0 to 10° C.) and high (e.g., 40 to 50°C.) temperatures. For accurate “gas gauging” under such conditions, theSmart Battery System (SBS) can also be employed. The SBS is part of acommercially available System Management Bus (SMB) system. The SBSallows battery packs to communicate to smart chargers and other systemintelligence using a physical protocol similar to the I²C bus protocolfrom Philips Corporation. The software protocol on the SMB allows fordirect communication of parameters such as the state of charge, batterypack voltage, battery temperature, number of discharge cycles, and soon. Several vendors of integrated circuits now offer single chipimplementations of the SMB interface. Alternatively, a custom programmedmicrocontroller, such as a PIC chip Microchip Technology Inc., can beused for this purpose.

[0153] In some embodiments, the device includes a power pack that isoptionally chargeable. In some other embodiments, the device optionallyincludes batteries such as, for example, four AA cells. The cellchemistries can vary. The device optionally accommodates alkalineinterchangeability.

[0154] The device optionally has a fitting for a secondary rechargeablepack that can be the same, or smaller, size as the power devicesdescribed above.

[0155] Specific Electronic-Nose Device Implementations

[0156] The e-nose device can be implemented in various configurations,to include various features, and be used in various applications. Somespecific implementations are provided below.

[0157] In one specific implementation, the e-nose device includes asensor array of 32 sensors, composed of conducting particles uniformlydispersed in a polymer matrix. Each polymer expands like a sponge whenexposed to a test medium (e.g., vapor, liquid, gas), thereby increasingthe resistance of the composite. The polymers expands to varying degreesbecause of their unique response to different analytes. This change inresistance varies across the sensor array, producing a distinctivesignature response. Regardless of whether the analytes correspond to acomplex mixture of chemicals in the test sample or from a singlechemical, the e-nose device includes sufficient polymer arrays toproduce a distinct electrical “fingerprint” for the samples of interest.The pattern of resistance changes in the sensor array is indicative ofthe identity of the analytes, while the amplitude of the patternindicates the concentration of the analytes.

[0158] The normalized change in resistance is then transmitted to aprocessor that identifies the type, quantity, and quality of the vaporbased on the detected pattern in the sensor array.

[0159] In another specific implementation, a portable e-nose device foruse in the field to detect volatile compounds is fabricated according tothe invention. The device incorporates an easy-to-read graphic LCD withback lighting and one or more light emitting diodes (LEDs) to indicatemode of operation. Communications ports are provided to enable easydownloading of data into a spreadsheet package. Rapid response tine,combined with easy one-button operation, provide an effective andaccurate measurement of the samples. Power is supplied by replaceable orrechargeable batteries. Housed in a robust, water-resistant case, theportable e-nose device is suitable for various environments.

[0160] In yet another specific implementation, the e-nose device isdesigned to acquire and store data collected from 32 independent sensorelements. The e-nose device includes a 32-channel sample chamber withinlet/outlet ports, a pump, a 3-way solenoid switch, a LCD, pushbuttons, LED, a humidity probe, a temperature probe, and a digitalinterface.

[0161] The power supply is designed for a 9-volt DC input. A rectifyingdiode is added for circuit protection. Two on-board 5-volt linearregulators are utilized for the analog and digital circuitry,respectively. A high precision buried Zener diode is provided to supplya +2.5 volt reference. The overall design is a mixed 3V and 5V designfor reduced power consumption in a handheld device.

[0162] The sample chamber houses 32 sensor elements deposited on fourceramic substrates, each with eight sensor elements. The substrates arefabricated using hybrid microelectronic co-fired ceramic (alumina)processes. Electrodes and contacts are deposited as thick films usingscreen-printing techniques. Resistive paths can be provided (e.g., threepaths) to be used as heating elements. On the backside of the substrate,a surface mount thermistor can be placed to form a heating/coolingcontrol loop.

[0163] An inlet port is provided and a baffle can be inserted to fan outthe incoming sample stream. The outlet port is respective to ambientbarometric pressures. The sample chamber can be fabricated of Teflon andis airtight, and is mount to the PCB. An on-board pump can push thesample flow into the sample chamber at pressures slightly higher than14.7 psi. The on-board 3-way solenoid switch can switch under processorcontrol between a known reference source (i.e., to “re-zero” orrecalibrate as necessary) and an unknown test sample. The four ceramicsubstrates are inserted in two 20-pin, 50-mil spacing, dual rowconnectors. The spacing between the rows is 100 mils. A temperatureprobe is inserted into one connector and a humidity probe is insertedinto the other. The temperature and humidity probes are used fordiagnostics.

[0164] A biasing network can been implemented that biases the chemicallysensitive resistor in a DC mode of operation. The network is aratiometric network that is easy to implement and stable, and offers awide dynamic range.

[0165] It has been shown that 50 PPM changes in electrical resistance ofthe chemically sensitive can be measured. Further, baseline changesgreater than ±50% can be accounted for with minimal change in appliedpower, as shown in Table 1. TABLE 1 Detectable Changes in Resistance forVarious Baseline Resistances Baseline Vout Applied Power Resolution 15K(−Δ50%) 0.326 0.047 18 bits 20K (−Δ33%) 0.417 0.043 18 bits 25K (−Δ17%)0.500 0.040 17 bits 30K, nominal 0.577 0.037 17 bits resistance 35K(+Δ17%) 0.648 0.034 17 bits 40K (+Δ33%) 0.714 0.032 17 bits 45K (+50%)0.776 0.030 17 bits

[0166] Assuming that Johnson noise is the dominant noise source, it ispossible to calculate an average noise voltage of 0.3 μV over a 10 Hzbandwidth and can thus detect these step changes. By keeping the currentlow (i.e., <25 μA) the 1/ƒ noise is reduced. In general, the biasingscheme is a constant voltage, DC system. The current is limited tomicro-amperes (μAs) per sensor element and the applied power is in theorder of micro-watts (μWs). For added flexibility the current is limitedand the output voltage is scaled by resistors.

[0167] The handheld sensing apparatus of the present invention was usedto sense a series of four (4) homologous ester analytes. The analytessensed were the ethyl esters of propionate, butyrate, valerate, andhexanoate. The response data was then analyzed using principal componentanalysis. Principal Component Analysis (PCA) is a powerful visualizationtool that provides a way to reduce the dimensionality of the data. PCAfinds linear combinations of the original independent variables thataccount for maximal amounts of variation and provides the best possibleview of variability in the independent variable block. Naturalclustering in the data is readily determined.

[0168]FIG. 15 shows a graph of a principal component analysis of theresponses to a series of esters using the handheld apparatus of thepresent invention. As shown in FIG. 15, the ester analytes were welldiscriminated by the handheld device of the present invention.

[0169] Analytes and Applications of the E-nose Device

[0170] Analytes detectable by the e-nose device of the inventioninclude, but are not limited to, alkanes, alkenes, alkynes, dienes,alicyclic hydrocarbons, arenes, alcohols, ethers, ketones, aldehydes,carbonyls, carbanions, heterocycles, polynuclear aromatics, organicderivatives, biomolecules, microorganisms, bacteria, viruses, sugars,nucleic acids, isoprenes, isoprenoids, and fatty acids and theirderivatives. Many biomolecules, such as amino acids, are amenable todetection using the sensor arrays of the invention.

[0171] The e-nose device can be used to enable medical and dentalcare-providers to quickly and accurately identify the chemicalcomponents in breath, wounds, and bodily fluids to diagnose a host ofillness including infections and metabolic problems. For example, thee-nose device can be used to test for skin conditions, for anesthesiaadministration, or to determine time of ovulation in fertilitytreatment. Alternatively, the handheld device can classify and identifymicroorganisms, such as bacteria.

[0172] The e-nose device can be used to locate an odor to identify acomplicated system or state of matter, and can offer versatility andreliability absent from conventional environmental or chemicalmonitoring devices. Advantageously, the device can be used for profilinga chemical environment in a hazardous materials situation and to assistemergency crews to accurately select fire retardant, containmentstrategies, and protective gear.

[0173] The e-nose device can be used to detect leaks in pipelines andstorage containers.

[0174] The e-nose device can be used in food quality and processingcontrol. For example, the device can be used to spot test for immediateresults or to continually monitor batch-to-batch consistency andspoilage in various stages of a product, including production (i.e.,growing), preparation, and distribution. The device can also be used indisposable packaging to providing an objectivity that is absent fromconventional spoilage, freshness, and contamination monitoringtechniques.

[0175] The e-nose device can also be used in protecting the elderly, whotend to lose sense of smell over time. The device can be used to reducethe risk of food poisoning or the ingestion of spoiled food, and can beintegrated with household appliances, such as refrigerators andmicrowave ovens.

[0176] The e-nose device can be used in a wide variety of commercialapplications including, but not limited to:

[0177] applications such as utility and power, oil/gas petrochemical,chemical/plastics, automatic ventilation control (cooking, smoking,etc.), heavy industrial manufacturing, environmental toxicology andremediation, biomedicine, cosmetic/perfume, pharmaceutical,transportation, emergency response and law enforcement,

[0178] detection, identification, and/or monitoring of combustible gas,natural gas, H₂S, ambient air, emissions control, air intake, smoke,hazardous leak, hazardous spill, fugitive emission, hazardous spill,

[0179] beverage, food, and agricultural products monitoring and control,such as freshness detection, fruit ripening control, fermentationprocess, and flavor composition and identification,

[0180] detection and identification of illegal substance, explosives,transformer fault, refrigerant and fumigant, formaldehyde,diesel/gasoline/aviation fuel, hospital/medical anesthesia &sterilization gas,

[0181] telesurgery, body fluids analysis, drug discovery, infectiousdisease detection and breath applications, worker protection, arsoninvestigation, personal identification, perimeter monitoring, fragranceformulation, and

[0182] solvent recovery effectiveness, refueling operations, shippingcontainer inspection, enclosed space surveying, product quality testing,materials quality control, product identification and quality testing.

[0183] It should be appreciated from the foregoing description that thepresent invention provides an improved vapor sensing instrument that notonly is sufficiently small and lightweight to be handheld, but also ismodular so as to allow the device to be conveniently adapted for use insensing the presence and identity of a wide variety of specified vapors.

[0184] Although the invention has been described in detail withreference to the presently preferred embodiments, those of ordinaryskill in the art will appreciate that various modifications can be madewithout departing from the invention. Accordingly, the invention isdefined only by the following claims.

What is claimed is:
 1. A handheld sensing apparatus comprising: ahousing; a sensor module mounted in the housing and including at leasttwo sensors that provide a distinct response to a particular testsample; a sample chamber defined by one or both of the housing and thesensor module, the sample chamber incorporating an inlet port and anoutlet port, wherein the at least two sensors are located within oradjacent to the sample chamber; and an analyzer mounted in the housingand configured to analyze a particular response from the at least twosensors, wherein the analyzer identifies or quantifies analytes withinthe test sample based on the particular response.
 2. The handheldsensing apparatus of claim 1 further comprising: a pump mounted in thehousing and configured to direct the particular test sample through thesample chamber, from the inlet port to the outlet port.
 3. The handheldsensing apparatus of claim 1 wherein the particular response includes aset of signals indicative of changes in resistances of the at least twosensors due to exposure to the particular test sample.
 4. The handheldsensing apparatus of claim 1 further comprising: measurement circuitrymounted in the housing and configured to detect the distinct responsefrom the at least two sensors and to provide a sensed signalcorresponding the distinct response.
 5. The handheld sensing apparatusof claim 4 wherein the measurement circuitry includes a sigma-deltaconverter.
 6. The handheld sensing apparatus of claim 1 wherein theanalyzer receives the distinct response from the at least two sensorsand generates a corresponding signature.
 7. The handheld sensingapparatus of claim 6 wherein a plurality of reference signatures iscollected for a plurality of reference samples and a sample signature isgenerated for the particular test sample, and wherein the analyzer isconfigured to compare the sample signature against the plurality ofreference signatures to identify the particular test sample.
 8. Thehandheld sensing apparatus of claim 1 further comprising: a valvemounted in the housing and configured to direct either a referencesample or an unknown test sample to the sample chamber.
 9. The handheldsensing apparatus of claim 8 wherein the reference sample ispreconditioned.
 10. The handheld sensing apparatus of claim 8 whereinthe reference sample is selected from among a plurality of referencesamples.
 11. The handheld sensing apparatus of claim 1 wherein thesample chamber is sealed from external environment, except for the inletport and the outlet port.
 12. The handheld sensing apparatus of claim 1further comprising a preconcentrator.
 13. The handheld sensing apparatusof claim 1 further comprising: thermal control circuitry that controlsthe temperature of the at least two sensors.
 14. The handheld sensingapparatus of claim 1 wherein at least one of the sensors in the sensormodule is a member selected from the group consisting of aconducting/nonconducting regions sensor, a SAW sensor, a quartzmicrobalance sensor, a conductive composite sensor, a chemiresitor, ametal oxide gas sensor, an organic gas sensor, a MOSFET, a piezoelectricdevice, an infrared sensor, a sintered metal oxide sensor, a Pd-gateMOSFET, a metal FET structure, a electrochemical cell, a conductingpolymer sensor, a catalytic gas sensor, an organic semiconducting gassensor, a solid electrolyte gas sensors, and a piezoelectric quartzcrystal sensor.
 15. The handheld sensing apparatus of claim 14 whereinat least one of the sensors in the sensor module is aconducting/nonconducting regions sensor.
 16. The handheld sensingapparatus of claim 14 wherein at least one of the sensors in the sensormodule is a SAW sensor.
 17. The handheld sensing apparatus of claim 1wherein the sensor module includes: a plurality of sensor array devices,each sensor array device including an array of sensors.
 18. A handheldsensing apparatus comprising: a housing including a receptacle; a sensormodule removably mounted in the receptacle of the housing, the sensormodule including at least one sensor that provides a distinct responseto a particular test sample; a sample chamber defined within the sensormodule, the sample chamber incorporating an inlet port and an outletport, wherein the at least one sensors is located within or adjacent tothe sample chamber; and an analyzer mounted in the housing andconfigured to analyze a particular response from the at least twosensors, wherein the analyzer identifies or quantifies analytes withinthe test sample based on the particular response.
 19. The handheldsensing apparatus of claim 18 further comprising: one or more additionalsensor modules, each sensor module configured to be removably mounted inthe receptacle and to incorporate at least one sensor, wherein eachsensor module is configured to provide a different set of responses to aset of distinctive samples.
 20. The handheld sensing apparatus of claim19 wherein each removably mounted sensor module includes an identifierfor identifying the sensor module, and wherein the analyzer isconfigured to determine the identifier included in the particular sensormodule received in the receptacle.
 21. A sensor module configured foruse with a sensing apparatus disposed within a housing that defines areceptacle, the sensor module comprising: a casing sized and configuredto be received in the receptacle of the sensing apparatus; a samplechamber; an inlet port configured to be releasably engageable with afirst port connection of the sensing apparatus when the sensor module isreceived in the receptacle, the inlet port receiving a test sample fromthe sensing apparatus and directing the test sample to the samplechamber; an outlet port configured to discharge the test sample from thesample chamber; at least one sensor located within or adjacent to thesample chamber and configured to provide a distinct response whenexposed to one or more analytes located within the sample chamber; andan electrical connector configured to be releasably engageable with amating electrical connector of the sensing apparatus when the sensormodule is received in the receptacle, the electrical connectortransmitting the characteristic signals from the at least one sensor tothe sensing apparatus.
 22. The sensor module of claim 21 wherein theoutlet port is configured to be releasably engageable with a second portconnection of the sensing apparatus when the sensor module is receivedin the receptacle of the sensing apparatus, the outlet port dischargingthe test sample from the sample chamber to the sensing apparatus. 23.The sensor module of claim 22 wherein the casing incorporates a rearwall that supports the inlet port, the outlet port, and the electricalconnector.
 24. The sensor module of claim 21 further comprising: asubstrate to which the plurality of sensors mounts.
 25. The sensormodule of claim 21 wherein the at least one sensor is arranged in auniform manner within the sample chamber.
 26. The sensor module of claim21 wherein each of the at least one sensor is implemented with achemically sensitive resistor having a resistance that varies in aunique manner when exposed to one or more specified test samples; andthe sensing apparatus includes an analyzer that detects a set ofresistances of the at least one sensor and identifies the test samplebased on the detected set of resistances.
 27. A handheld sensingapparatus for measuring the concentration of one or more analytes withina sample chamber, comprising: at least two chemically sensitiveresistors, each chemically sensitive resistor having a resistance thatvaries according to a concentration of one or more analytes within thesample chamber; conditioning circuitry coupled to the at least twochemically sensitive resistors, the conditioning circuitry generating ananalog signal indicative of the resistance of each of the at least twochemically sensitive resistors; an analog-to-digital converter (ADC)coupled to the conditioning circuitry, the ADC responsive to the analogsignal and providing a digital signal; and an analyzer coupled to theADC, the analyzer responsive to the digital signal and determining theidentity or concentration of one or more analytes within the samplechamber.
 28. The handheld sensing apparatus of claim 27 wherein theconditioning circuitry includes a set of voltage divider networks, onenetwork for each of the at least two chemically sensitive resistors,each network providing an analog voltage.
 29. The handheld sensingapparatus of claim 27 further comprising: at least one multiplexercoupled to the set of voltage divider networks, the multiplexer couplingthe analog voltage from the set of voltage divider networks to the ADC.30. The handheld sensing apparatus of claim 29 further comprising: atleast one amplifier, each amplifier coupled between one multiplexer andthe ADC.
 31. A hand-held vapor sensing apparatus, comprising: ahand-held housing; a sensor module mounted in the housing andincorporating a plug-in array of vapor sensors, each vapor sensorproviding a different electrical response to one or more distinctvapors; wherein one or both of the housing and the sensor module definea sample chamber to which the array of vapor sensors of the sensormodule is exposed, the sample chamber incorporating a vapor inlet and avapor outlet; a pump mounted on the housing and configured to direct avapor sample through the sample chamber, from the vapor inlet to thevapor outlet; a monitoring device mounted on the housing and configuredto monitor the electrical responses of the array of vapor sensorsincorporated in the sensor module, and further configured to produce acorresponding plurality of sensor signals; and an analyzer mounted onthe housing and configured to analyze the plurality of sensor signals,to identify any vapor sample directed through the sample chamber by thepump.
 32. A plug-in sensor module configured for use with a hand-heldvapor sensing apparatus of a kind including a hand-held housing thatdefines a receptacle, the sensor module comprising: a casing sized andconfigured to be received in the receptacle of the hand-held vaporsensing apparatus; a sample chamber; a vapor inlet configured to bereleasably engageable with a first vapor connection of the hand-heldvapor sensing apparatus when the plug-in sensor module is received inthe receptacle of the vapor sensing apparatus, for receiving a vaporsample from the vapor sensing apparatus and directing the vapor sampleto the sample chamber; a vapor outlet configured to discharge the vaporsample from the vapor chamber; and a plurality of vapor sensors locatedwithin or adjacent to the sample chamber and configured to providedifferent electrical signals in response to one or more vapors locatedwithin the sample chamber; an electrical connector configured to bereleasably engageable with a mating electrical connector of thehand-held vapor sensing apparatus when the plug-in sensor module isreceived in the receptacle of the vapor sensing apparatus, to transmitelectrical signals from the plurality of vapor sensors to the vaporsensing apparatus.
 33. A vapor sensing apparatus for measuring theconcentration of one or more prescribed vapors within a sample space,comprising: a chemically sensitive resistor having a resistance thatvaries according to the concentration of one or more prescribed vaporswithin a sample space; a reference resistor connected in series with thechemically sensitive resistor, between a reference voltage source andground, such that an analog output signal is established at the nodebetween the reference resistor and the chemically sensitive resistor; ananalog-to-digital converter, responsive to both the analog output signaland the voltage level of the reference voltage source, for producing adigital output signal indicative of the resistance of the chemicallysensitive resistor; and an analyzer, responsive to the digital outputsignal, for determining the concentration of one or more prescribedvapors within the sample space; wherein the vapor sensing apparatus isconfigured such that variations in the voltage level of the referencevoltage source will have only an insubstantial effect on the value ofthe digital output signal.